China Safety Science Journal

Research on civil aviation security event analysis based on deep LSTM model

FENG Wengang

2021, 31(9): 1-7. doi:10.16265/j.cnki.issn1003-3033.2021.09.001

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In order to assist police officers to analyze civil aviation security events, deep LSTM model was used to study subject identification of these events. Firstly, multi-modal information of them was presented by establishing a database, and their time series characteristics were extracted. Then, a deep LSTM model was developed to study and predict subjects of security events. The results show that the proposed model can predict subjects more accurately based on time series characteristics of the events, and even in the presence of noise, it can obtain better prediction results. Moreover, related research results have been successfully applied in SZX international airport.

STPA safety analysis on IMA generic system management

XIAO Guosong, LIU Jiachen, DONG Lei, SUN Zijing, ZHAO Changxiao

2021, 31(9): 8-14. doi:10.16265/j.cnki.issn1003-3033.2021.09.002

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GSM is an indispensable part of IMA system services. In order to address the difficulties traditional safety analysis methods have in capturing risks caused by component interaction in complex systems, firstly, GSM work environment and function division of its components were studied, and workflow of hierarchical system management was determined. Secondly, an extended model based on accident process of systematic theory was established for GSM, unsafe control actions(UCA) of dynamic reconfiguration case were identified through STPA, and relevant causative scenarios and their corresponding safety requirements were generated. Finally, the case is simulated and verified by timed automata. The results show that the model's logic and timing integrity and reachability of UCA behavior provide a formal basis for GSM safety analysis.

Construction and application of third-party risk model for unmanned aerial vehicle operation in urban environment

REN Xinhui, CHENG Caixia

2021, 31(9): 15-20. doi:10.16265/j.cnki.issn1003-3033.2021.09.003

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In order to quantify risks of UAV operation in urban areas, the third-party risk sources and their mechanism of action were analyzed. Then, a third-party risk model for UAV city operation, considering noise and safety factors comprehensively, was established based on privacy image grids. Finally, with Tianjin People's Park in Hexi District as a sample scenario, risks of UAV operation in the airspace 30-60 meters above it were evaluated. The results show that risks are decreasing as UAV flying altitude above buildings and entertainment areas is increasing. However, in other areas such as lakes, woods, roads, open spaces, risks increase along with the increase of flying altitude. When at the same height, risk above lakes and greenery is the lowest, followed by that above buildings and open squares, and then the highest above entertainment areas.

Research on key index system and risk evaluation model of enterprise work safety

YAN Hongqiao, CHEN Yiyue, TIAN Kun, HU Jinqiu, MAO Yaming, ZHOU Jingtong

2021, 31(9): 21-28. doi:10.16265/j.cnki.issn1003-3033.2021.09.004

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In order to perform a comprehensive and real-time objective evaluation of the status quo of enterprise work safety and to avoid deviation caused by manual intervention in traditional risk evaluation methods, firstly, a barrier-consequence hierarchical key indicator system was proposed according to accident cause theory, and indicators were quantified through mining structured data such as accidents and unstructured data such as checking text. Then, PCA and EW were adopted for data dimensionality reduction and risk evaluation, and exponential smoothing method was used to predict risk level of enterprises in the next cycle before an risk evaluation and early warning model was established. Finally, the model was applied to two oil and gas production enterprises. The results show that this risk evaluation model can accomplish assessment of current risks and prediction of risks in future cycles through acquisition, processing and learning of barrier-consequence historical data, and provide guidance for enterprises' safety management (risk reduction, risk elimination, and that of chemical hazard barriers, etc.).

Research on relationship between work stress and safety performance of senior managers in coal mines

HE Qi, ZHANG Jinsuo, WANG Ping

2021, 31(9): 29-35. doi:10.16265/j.cnki.issn1003-3033.2021.09.005

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In order to explore relationship between work stress and safety performance of senior coal mine managers, a hypothetical relationship of work stress directly affecting safety performance was put forward, and emotional labor and work engagement were considered as intermediary variables. Then, 331 senior managers were investigated by using work stress scale, emotional labor scale, work engagement scale and safety performance scale, and the data were analyzed and tested by utilizing SPSS25.0 and AMOS23.0 software. The results show that their work stress has a significant negative impact on safety performance, with different stress source dimensions resulting in different influencing scale and significance on safety performance. And emotional labor and work engagement have obvious mediating and chain mediating effects between work stress and safety performance.

Study on creep disturbance characteristics of sandstone considering initial damage effect

SU Ronghua, LI Chao, MA Zhiyuan

2021, 31(9): 36-43. doi:10.16265/j.cnki.issn1003-3033.2021.09.006

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In order to study creep characteristics of sandstone with initial damage under disturbance action, four kinds of working conditions were designed, and uniaxial compression creep disturbance test was carried out by using self-made creep test device.Considering influence of initial damage and accelerated creep damage, a nonlinear creep model of rock was constructed by introducing plastic deformation body, accelerated damage element and Burgers model in series. Creep parameters were inversed by used Levenberg-Marquardt+general global optimization method. The results show that there is a stress threshold for disturbance effect, and after reaching threshold, there is an obvious strain mutation in the creep curve before and after disturbance. Instantaneous elastic modulus under different working conditions has a similar trend of first rising and then decreasing, but instantaneous elastic modulus of specimen with initial damage is significantly lower than that of intact group. Long-term strength of sandstone with initial damage under disturbance condition decreases significantly, which is far less than same value. Long-term strength of intact specimen under disturbance condition is only 60%-64% of corresponding uniaxial compressive strength, and experimental data are in good agreement with theoretical curve of model, which can better reflect creep disturbance characteristics of sandstone with initial damage.

Effect of heating mode on thermal runaway behavior of lithium ion battery

ZHANG Qingsong, LIU Tiantian, BAI Wei

2021, 31(9): 44-51. doi:10.16265/j.cnki.issn1003-3033.2021.09.007

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In order to investigate safety of lithium-ion batteries under different heating conditions in the process of transportation and use, thermal runaway of battery was caused by a cylindrical heating rod and a spring heating ring at a temperature rise rate of 5 and 10 ℃/min respectively, and experimental phenomenon and data were studied. Thermal runaway gas was sampled and gas composition was analyzed. The results show that thermal runaway process of battery all goes through heat storage stage, exhaust stage and thermal runaway stage. At 5 and 10 ℃/min, time of thermal runaway caused by spring heating ring is 18.3% and 40.2% faster than that of heating rod, respectively, and the maximum temperature in the thermal runaway stage decreased by 11.2 and 24.6 ℃, respectively. When battery is heated by heating rod, combustion is more sufficient, and the maximum thermal runaway temperature of battery decreases with the increase of temperature rising rate of heating device.

Diagnosis of safety operation state for ATC position based on four diagnostic methods

YUE Rentian, HAN Meng

2021, 31(9): 52-59. doi:10.16265/j.cnki.issn1003-3033.2021.09.008

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In order to ensure safety operation of air traffic, based on four diagnostic methods of traditional Chinese medicine, diagnostic index system of safety operation state for ATC position was constructed from four aspects of observation, auscultation and olfaction, inquiry, pulse feeling and palpation. Combining combination weighting method, set pair analysis and BP neural network, a combination diagnosis method with self-learning ability was proposed. Firstly, weight required by set pair analysis was obtained by combination weighting method. Secondly, operation state of ATC position in each sample was obtained by set pair analysis. Finally, BP neural network was trained and tested based on samples, and operation state diagnosis the model was obtained. The results show that the model is simple and easy to use, and diagnosis results are accurate, and it has advantages of combining qualitative and quantitative.

Intelligent early warning system of gas and coal spontaneous combustion disaster based on big data: data characteristics, application structure and key technologies

ZHANG Jufeng, SHI Shiliang, LU Yi, YOU Bo, WU Fanghua, WU Kuan

2021, 31(9): 60-66. doi:10.16265/j.cnki.issn1003-3033.2021.09.009

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In order to solve problem of multi-source, massive, dynamic and complex information processing in the process of symbiotic disaster early warning, data characteristics, application architecture and key technologies of big data intelligent early warning system of gas and coal spontaneous combustion were analyzed by applying big data driven technology, application architecture of big data driven symbiotic disaster early warning system was built, and key of symbiotic disaster intelligent early warning lies in big data acquisition, integration, analysis application and early warning technology was discussed. The research results show that big data driven technology has strong insight, decision-making power and process optimization ability in the intelligent early warning of mine gas and coal spontaneous combustion symbiosis disaster, which can process massive monitoring data of symbiotic disaster timely and efficiently, extract valuable knowledge, and realize the construction of application architecture of symbiotic disaster big data intelligent early warning system.

Shaft lining vibration and surrounding rock damage control after freezing shaft blasting

FU Xiaoqiang, YU Jin

2021, 31(9): 67-74. doi:10.16265/j.cnki.issn1003-3033.2021.09.010

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In order to address problems of shaft lining vibration and surrounding rock damage caused by blasting of freezing shaft, shaft lining vibration was monitored in real time and frozen walls' formed images after blasting were taken. Then, TQWT (Tunable Q-factor Wavelet Transform) was used to refine features of vibration signals, ACM (Active Contour Model) and RFA(Random Forest Algorithms) were adopted to analyze shaping effect of surrounding rock for controlled blasting with slotted cartridge charge, and feature recognition and scientific classification of rock images under different blasting conditions were carried out. The results show that vibration of shaft lining and damage of surrounding rock can be effectively reduced by optimizing blasting parameters. Controlled blasting technology with slotted cartridge charge has effects of vibration reduction, shaft lining protection and damage reduction, and the higher Prussian coefficient of rock is, the better application effect of slotted charge blasting will be.

Simulation study on gas explosion induced by gas leakage of urban buried gas pipelines

WANG Qiuhong, WANG Liwen, JIANG Juncheng, ZHANG Mingguang, LI Xin

2021, 31(9): 75-82. doi:10.16265/j.cnki.issn1003-3033.2021.09.011

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In order to explore overpressure and temperature characteristics of explosion flow field after gas leakage of buried natural gas pipelines, FLACS was used to simulate leakage and explosion accidents of pipelines. Then, development characteristics of these accidents were studied from three aspects, environmental wind speed, leak rate, and leakage aperture. The results show that under a condition of continuous and stable leakage, flammable gas's coverage area will be stable. Wind speed, leakage aperture and leak rate influences buoyancy dispersion stage, jet nucleus, and initial momentum respectively, thus influencing gas dispersion. When an accident happens, explosion flame mainly propagates upward, and the overpressure it generates is comparatively small, but the temperature is high. Under windless condition, when leakage aperture is 0.3 m, leak rate at 4 kg/s, overpressure of gas cloud explosion generated by leakage is 0.46 kPa, while high temperature generated reaches as high as 2 135.7 K.

Nuclear magnetic resonance experimental study on pore characteristics of high rank coal with different bedding

LIU Jiajia, HU Jianmin, YANG Ming, FANG Yingxiang, JIA Gaini

2021, 31(9): 83-89. doi:10.16265/j.cnki.issn1003-3033.2021.09.012

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In order to study pore distribution characteristics of high rank coal with different bedding, NMR experiments were carried out under different centrifugal forces of saturated coal samples. Firstly, three high rank coals with parallel bedding and three vertical bedding were selected. Then, T₂ pattern and NMR porosity of saturated coal samples under different centrifugal forces were measured by low field NMR system. The results show that adsorption pores are the most developed in high-rank coal, followed by seepage pores and cracks. Water in large pores and cracks of coal samples is easy to be ejected under centrifugal force, but water in tiny pores is difficult to be ejected. Parallel and vertical stratification of coal sample with the increase of centrifugal force, peak, peak area of T₂ spectrum and nuclear magnetic porosity have been gradually decreases, parallel and vertical stratification of coal sample nuclear magnetic accords with exponential function relationship between porosity and centrifugal force. T_2C (T₂ cutoff value) vertical stratified coal sample is 1.44 times that of parallel stratified coal sample. T_2C of vertical stratified coal sample increases with the increase of centrifugal force, while T_2C of parallel stratified coal sample increases first and then decreases with the increase of centrifugal force.

Impacts of ignition position on secondary explosion outside vessels

MA Qiuju, SHAO Juncheng, WAN Mengsai, WANG Legeng, Wang Wei

2021, 31(9): 90-98. doi:10.16265/j.cnki.issn1003-3033.2021.09.013

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In order to prevent external explosion induced by methane explosion venting, numerical simulation of explosion venting process was carried out by using Simtec software for different ignition positions, including front ignition, central ignition and rear ignition. Then, phenomena of secondary explosion were observed and simulation data were analyzed. The results show that better "pressure relief" effect can be achieved by setting the rupture disc, but explosion venting induces secondary explosion outside vessels, which needs to be focused on and prevented. Pressure of measuring points inside containers will approach to peak value when the second peak value caused by secondary explosion occurs at point 6 in explosion vent hole. Ignition position directly affects amount of unburned methane released during explosion venting, and thus impacts secondary explosion intensity. As a result, secondary explosion comes as the strongest for the case with rear ignition, followed by central ignition and front ignition which is the weakest one. The closer it is to explosion vent, the weaker external secondary explosion intensity will be. Therefore, explosion vent should be located close to the areas prone to have an ignition source.

Study on fire behavior characteristics and it's burn-through capability to cargo liner in dynamic pressure cargo compartment

WANG Wei, WANG Jian, WANG Libin, YANG Juntao, ZHANG Yongfeng

2021, 31(9): 99-105. doi:10.16265/j.cnki.issn1003-3033.2021.09.014

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In order to explore control effect of dynamic pressure caused by depressurization on fire behavior and mechanism on the burn-through ability and enhance fire prevention capability, nearly real emergency dynamic variable pressure environment was constructed, a series of fire resistance tests of oil pools and fire lining were carried out. The results show that depressurization could increase flame height and raise high temperature area, resulting direct contact between flames and cargo compartment ceiling. Cargo liner limited flame height, air entrainment and hot air escape. Raised flame forms jet fire below cargo liner, increased contact area between flame and cargo liners, and enhanced thermal feedback. The decreased mass burning rate led to longer burning time and contact time between flame high temperature area and cargo liner, burned expansion area and carbonized area of cargo liner are larger, and more serious burning damage.

Aerodynamic response analysis of unmanned aerial vehicle rotor hovering under crosswind influence

LIU Cong, WEI Zhiqiang, HAN Hongrong, SHAN Zezhong

2021, 31(9): 106-112. doi:10.16265/j.cnki.issn1003-3033.2021.09.015

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In order to ensure precise control and safety of UAV's hover state under crosswind influence, time-averaged and unsteady aerodynamic responses of UAV's rotor with different crosswind speeds were studied by wind tunnel experiment and numerical simulation. Firstly, influence of crosswind speed on time-averaged thrust and torque of rotor was measured by wind tunnel experiment, and then coefficients of rotor dynamic model under different wind speeds were fitted. Then, aerodynamic unsteady effect of a rotor in a rotation period was discussed by numerical simulation. Finally, vorticity field and velocity field were compared under crosswind speed conditions. The results show that crosswind can significantly increase rotor's tension and torque, but high wind speed will lead to low hovering efficiency. When wind speed is high, unsteady aerodynamic effect of rotor can not be ignored, and it is necessary to consider crosswind action and unsteady aerodynamic response when controlling hover state. Crosswind also helps to enhance vortex intensity and induce velocity of rotor downwash vortex.

Quantitative evaluation method of blast-resistant and defense loads for VCE in petrochemical process

XIN Baoquan, DANG Wenyi, YU Jianliang, WANG Xige, YAN Xingqing, LU Wei

2021, 31(9): 113-118. doi:10.16265/j.cnki.issn1003-3033.2021.09.016

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In order to reasonably determine VCE defense load in multiple scenarios of complex petrochemical process, a quantitative assessment method was established based on risk acceptance criteria and blast resistant and defense requirements. Firstly, leakage units were divided according to dangerous process flow, and explosion frequency was calculated. Then, based on multi-energy method from Netherlands Organization for Applied Science, overpressure and duration of 720 potential explosion scenarios were calculated. Finally, VCE defense load of a petrochemical plant control room was determined quantitatively depending on two proposed criteria. The results show that a reasonable load should simultaneously satisfy risk acceptance criterion of cumulative frequency at 1×10^-5 to 1×10^-4 times/a and maximum stability criterion of explosion overpressure. Explosion scenarios, frequency, volume of blocking area and distance away from explosion source are key variables affecting VCE load. The proposed method can filter out impacts of high consequence and low probability scenarios on final VCE defense load, and meanwhile avoid randomness of its calculation results caused by discrete selection of scenes.

Interval prediction of mining work safety situation based on fuzzy information granulation

WU Menglong, YE Yicheng, HU Nanyan, WANG Qihu, LI Wen, JIANG Huimin

2021, 31(9): 119-127. doi:10.16265/j.cnki.issn1003-3033.2021.09.017

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In order to improve prediction accuracy of mining work safety situation, aiming at problems of low prediction accuracy and difficult model selection for non-stationary nonlinear time series by a single prediction model, a mining work safety situation interval prediction model based on FIG was proposed. Firstly, time series of mining work safety situation was mapped into fuzzy information granules containing three parameters: L, R and U. Then, ARIMA model was used to predict linear part of fuzzy particle sequence to obtain a nonlinear residual sequence. Finally, nonlinear residual sequence was used as an input variable to establish a SVM model, and prediction result of ARIMA model was superimposed with residual sequence prediction value of SVM model to obtain interval of mining work safety situation time series predictive value. The results show that accuracy of interval prediction model based on FIG is verified by 21 test sets of samples, average relative errors of L, R and U are 10.834 57%, 20.207 90% and 0.651 97%, respectively, fitting effect of interval prediction model of mining work safety situation based on fuzzy information granulation is better than ARIMA and SVM, with higher accuracy and reasonable interval range.

Critical slowing down characteristics of acoustic emission of gas bearing coal under unloading conditions

ZHANG Ran, LIU Jie, SA Zhanyou, CHENG Jianwei, LU Shouqing, WANG Chunyuan

2021, 31(9): 128-134. doi:10.16265/j.cnki.issn1003-3033.2021.09.018

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In order to obtain effective precursor information of instability failure of coal sample under unloading conditions, a fixed axial stress unloading confining stress experiment under different gas pressures was designed, and AE results of coal sample fracture process were obtained, and critical slowing down characteristics of AE time series under different gas pressures were calculated, so as to provide early warning of occurrence of coal and rock gas dynamic disasters. The results show that under unloading conditions, AE time series of gas-bearing coal has critical slowing characteristics. Sudden increase of variance and autocorrelation coefficient before coal sample failure can be used as precursor information to characterize failure of sample. Window length and lag step can affect critical slowing down characteristics. In contrast, variance is less affected by window length and lag step, and curve changes smoothly before precursor information appears.

Orthogonal experiment design and range analysis of TPCT extracting thermal energy from coal fire

ZHONG Kaiqi, XIAO Yang, LU Xing,DENG Jun

2021, 31(9): 135-141. doi:10.16265/j.cnki.issn1003-3033.2021.09.019

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In order to investigate influence of three main factors, such as concentration of CuO working medium, insertion depth and inclination angle, on the extraction performance of coal thermal energy. Three levels were selected to form L9 orthogonal test, extraction test of coal thermal energy by TPCT was carried out when temperature of coal body was 100 ℃. According to range analysis of test results, it can be concluded that under test conditions, order of influencing factors affecting extraction of TPCT coal thermal energy is inclination > concentration of nano-CuO working fluid> insertion depth. The optimal scheme is determined with mass fraction of nano-CuO as 5%, insertion depth as 40 cm and inclination angle as 90°. According to repeatability test of this scheme, it is found that the maximum cooling rate under this scheme is 38.62%, which is better than results of 9 groups of orthogonal tests. Based on above tests and analysis, the optimal factor level of TPCT in the extraction of coal fire heat energy is determined, and the optimal extraction effect is obtained under factor level.

Modeling and simulation of cruise emergency evacuation process for layout optimization

YU Ping

2021, 31(9): 142-149. doi:10.16265/j.cnki.issn1003-3033.2021.09.020

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In order to improve evacuation efficiency of cruises after emergencies and to optimize their spatial layout, an evacuation model, including spatial topological relationship model and tourist evacuation behavior model, was constructed. Then, with certain cruise as an example, optimization suggestions were put forward based on simulated evacuations under different scenarios. The results show that the bottleneck of cruise evacuation lies in stairs, and increasing stair width can improve evacuation efficiency, but not indefinitely. It has more significant effects to improve efficiency by increasing flow velocity of staircases than that of floors. And an increase in evacuation exits can also raise overall efficiency, but such increase magnitude is related to exit locations and tourist distributions. Better evacuation can only be achieved when exits can evenly serve tourists.

Network analysis on causes for serious traffic accidents based on text mining

HAN Tianyuan, TIAN Shun, LYU Kaiguang, LI Xuan, ZHANG Jiatao, WEI Lang

2021, 31(9): 150-156. doi:10.16265/j.cnki.issn1003-3033.2021.09.021

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In order to study characteristics of serious traffic accidents so as to effectively prevent them and reduce injuries, 254 investigation reports of such accidents were processed by text mining technology. Then,32 high-weight keywords were extracted by using improved term frequency-inverse document frequency (TF-IDF) algorithm. Finally, a hierarchical model of traffic accident mechanism, based on network centrality analysis, core edge structure analysis and agglomerative subgroup analysis on accident causes, was constructed considering theory of human vehicle road system safety. The results show that the contribution values of serious road traffic accidents network rank as illegal behavior, potential safety hazards and improper operation from top to bottom, and in terms of illegal behavior, it goes in the order of overload, speeding, wrong lane use, and fatigue, etc. The coupling of direct causes for illegal behavior and improper operation with indirect ones for potential safety hazards constitute the fundamental reason for failure of safe operation system in major accidents.

Bibliometric analysis on cup burners based on scientometric mapping

ZHAO Chenyu, ZHANG Tianwei, ZHANG Guiyun, GUO Zidong

2021, 31(9): 157-166. doi:10.16265/j.cnki.issn1003-3033.2021.09.022

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To analyze development trend of cup burners, a thorough bibliometric and scientometric mapping network analysis was conducted by utilizing VOSviewer on 322 cup burner related documents collected from Web of Science Core Collection. The results show that attention on cup burners and related field is increasing worldwide. Among 34 countries involved, China features the largest number of publications in this field, accounting for 40% of the total, and it pays continuous attention to it. And Liao Guangxuan is the most productive author with the largest number of papers, and a large collaboration network has been formed with him as the center. Through analysis on research hot-spots, it is found that studies on micro-level of diffusion flame in cup burners may become a trend, and extinguishing agent will develop a composite type. Therefore, it is necessary to make some improvement on cup burners for them to adapt to ever-evolving extinguishing agent form.

Comprehensive assessment and spatial pattern study on forest fire risk in Yunnan Province

LONG Tengteng, YIN Jiyan, OU Zhaorong, YANG Qiang, LI Yong, WANG Qiuhua

2021, 31(9): 167-173. doi:10.16265/j.cnki.issn1003-3033.2021.09.023

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In order to effectively reveal spatial heterogeneity and relevance of forest fire risk, and provide a scientific reference for allocation and regional linkage of fire prevention and control resources,take the natural factors and the human factors into consideration comprehensively,entropy method and comprehensive index method were used to assess forest fire risk in Yunnan province. Then, spatial pattern of the risk was studied by utilizing spatial auto correlation model. The results show that the risk of forest fire in western Yunnan is higher than that in the east, and most areas feature higher risk and high risk level, especially in northwest, west and central part. There are two fire risk trend lines, one extending from the northwest along the middle part to the northeast, which demonstrates a trend of high at both ends and low in the middle. The other one is low in the north and south, and high in the middle. The fire risk shows spatial agglomeration in space, but its degree of significance is average with weak local correlation.

Experimental study on influence of coal mining on seismic performance of RC frame structure

BAI Chun, WANG Laigui, LIU Shuxian, LU Shasha, NIE Wei

2021, 31(9): 174-183. doi:10.16265/j.cnki.issn1003-3033.2021.09.024

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In order to study seismic performance degradation characteristics of goaf edge buildings under influence of coal mining,RC frame structure at the edge of goaf was taken as research object, factors such as surface subsidence, non-uniform settlement of buildings and seismic force under coal mining disturbance were considered. Mining simulation test bench was designed to simulate bidirectional non-uniform settlement of buildings under the four working conditions of 0, 2, 4 and 6 mm/m. Based on theory of uniform similarity rate, a scaling model with a similarity ratio of 1/10 was designed to conduct dynamic test under action of El-Centro waves at the intensities of 7 and 8 degree. Natural frequency of model was obtained by white noise sweep, and dynamic responses such as acceleration amplification coefficient, interlaminar deformation, energy time-history response, strain response, failure characteristics of model structure were studied. The test results show that under influence of mining, buildings had different degrees of initial damage, which are mainly concentrated at the bottom of the structure. In the effect of earthquake, the greater the influence of mining, the more significant the structural dynamic response increases, and the greater the structural stiffness reduction. When intensity of earthquake increases, plastic damage and deformation increase, and structural rigidity decreases sharply, and weak layer expands to the upper layer in the working conditions with large mining influence.

Discussion on structural type of emergency rescue station without evacuation conditions outside tunnels

LI Chunhui, WANG Mingnian, GUO Xiaohan, LIU Kerui, YU Li

2021, 31(9): 184-190. doi:10.16265/j.cnki.issn1003-3033.2021.09.025

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As current emergency rescue station structure cannot meet requirements of evacuation and rescue, and there is no evacuation conditions outside tunnels, a new structural type of rescue station is proposed. With a railway tunnel project as an example, numerical simulation was conducted by using FDS5.0 software to analyze smoke diffusion process of burning trains under influence of train fire position, tunnel longitudinal slope and longitudinal ventilation wind speed. Then, relevant structure parameters of emergency rescue station were determined. The results show that the new structure shall include three parts, evacuation area, isolation region and avoidance rescue area. Longitudinal wind speed has the greatest influence on length of smoke diffusion, followed by slope, and finally train fire location. It is recommended that length of isolation zone on the downhill side is set at 1 350 m, and that on uphill side at 1 450 m.

Modeling effect of walking speed and load on muscular fatigue for dynamic tension work

TANG Fan, YI Cannan, LI Kaiway, ZUO Huali, YIN Lixia, LI Wanqi

2021, 31(9): 191-196. doi:10.16265/j.cnki.issn1003-3033.2021.09.026

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In order to investigate effect of walking speed and load on muscular fatigue for dynamic tension work, and models for predicting muscular fatigue was constructed, a simulated dynamic truck pulling work was designed and 10 male college students were recruited as participants. Then, MVC before and after the test and MET were measured, and RPE of multiple body parts were recorded, effects of speed and load on variation of tension, MET and RPE was investigated. Also, predict MET model was constructed based on data. The results show that walking speed affects MET, tension attenuation value(ΔF), DFD and RPE for multiple parts of body significantly, while load effect MET remarkably. Prediction model is reasonable to describe relationships between MET and load intensity and walking speed, and had a lower deviation between prediction values and actual values when compared with other MET prediction models. It was more suitable for prediction and assessment of muscular fatigue in dynamic truck pulling task.

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